Spacecraft Skims Venus Atmosphere for Science

by SPACE.com Staff | April 23, 2010 05:12pm ET

Starting its scientific surveying in July 2006, the European Space Agency's(ESA) Venus Express has been carrying out the most detailed study of the planet's thick and complex atmosphere to date.Credit: ESA

A European-built spacecraft has used its solar wings as
sails to skim through the sweltering atmosphere of Venus at the planet's
outermost border with space.

The European Space Agency's (ESA) Venus Express spacecraft
conducted five "aerodrag" maneuvers last week, which used the orbiter
as a sensor capable of very accurately measuring the atmospheric density just 111
miles (180 km) above the cloud-enshrouded
planet.

To do these aerodrag measurements, the solar panels of Venus
Express were rotated through five sets of orientations, which changed daily, to
exposed the wings to the vanishingly faint wisps of Venus'
atmosphere at its boundary with space.

The solar wing configuration generated a tiny but measurable
amount of aerodynamic torque, or rotation, on the probe. This torque can be
measured very accurately based on the amount of correction that must be applied
by reaction wheels, which counter-rotate inside the spacecraft to maintain its
orientation in space.

That correction data, in turn, tells scientists just how
thick or thin the atmosphere
of Venus is at the point the spacecraft was during the maneuver.

On the last day of the aerodrag campaign, which ended on
April 16, the solar arrays were rotated at plus and minus 45 degrees to the
atmospheric flow, mimicking the vanes of a windmill. They maneuver allowed
Venus Express to gather more information on the behavior of the molecules of Venus'
atmosphere as they bounced off the probe's solar wings.

"The aerodrag campaign went without problem, and
conclusively demonstrated that Venus
Express can be securely and accurately used to sense the density of the
planet's atmosphere," said Octavio Camino, the probe's spacecraft
operations manager. "Venus Express has shown once again that it is a very
capable satellite."

Camino said that the mission operations team will study last
week's results to develop an optimised configuration for aerodrag campaigns in
October and in 2011. Aerodrag testing was also conducted in 2008, 2009 and
February 2010.

Continued positive results may enable Venus Express to
conduct more sophisticated investigations deeper in the atmosphere, which would
be of immense interest to planetary scientists.

The spacecraft launched toward the cloud-covered second
planet of the solar system in 2005 and arrived at Venus
a year later. The mission was extended for four months in May 2009, and then
received another reprieve in September 2009 ? this time, extending the mission
to 2010.

Aerobraking demonstrations are expected to follow through at
least 2011 or 2012, ESA officials have said.